A passive optical network (PON) can deliver voice, video and other data among multiple network nodes, often referred to as optical network terminals (ONTs), using a common optical fiber link. Passive optical splitters and combiners enable multiple ONTs to share the optical fiber link. Each ONT terminates the optical fiber link for a residential or business subscriber, and is sometimes referred to as a subscriber premises node. Each ONT is connected to one or more subscriber devices, which ultimately receive the voice, video and other data delivered via the PON.
Generally, a PON includes a PON interface, sometimes referred to as an optical line terminator (OLT), having multiple, independent PON interface modules that serve multiple optical fiber links. A PON interface module provides an interface for transmission and reception of data packets over a particular optical fiber link that serves a group of ONTs. A PON is inherently a downstream-multicast medium. Each packet transmitted on an optical fiber link can be received by every ONT served by that link. ONTs identify selected packets on the fiber link based on addressing information included within the packets.
An ONT on a PON may receive traffic from several sources. Some sources may be commonly used among several ONTs on a PON. For example, several ONTs may access a common traffic flow associated with switched digital video (SDV) or other multicast streams. Other sources may produce traffic flows that are unique to an individual ONT. For example, an individual ONT may receive web content from an Internet service provider (ISP) or voice data from the public switched telephone network (PSTN).
ONTs generally receive common traffic flows at a common transmission rate. However, the bandwidth capacity of the ONT may limit throughput of the ONT, e.g., to 100 mega-bits per second (Mbps). Consequently, access to two or more traffic flows may exceed the bandwidth capacity of a given ONT, causing the ONT to be overrun.